Beyond thiols, beyond gold: Novel NHC-stabilized nanoclusters in catalysis

在2022财年，我们与Tsukuda和Hakkinen团队合作，成功合成了n -杂环碳烯（NHC）配体稳定的金纳米簇。我们证明了使用受bianp启发的手性NHCs来制备具有独特细长中心Au10核心的手性Au10纳米团簇。ESI-MS和单晶x射线晶体学证实分子式为[Au10(bisNHC)4Br2]2+。手性Au10纳米团簇采用线性边缘共享四面体几何形状，具有长形。该簇在CH2Cl2中的紫外可见光谱在291,325和546 nm处显示出四个突出的吸收带，这与双nhc双核Au(I)配合物的光谱有很大的不同。CD谱显示手性转移从手性铋配体到内部的Au10纳米簇核。ESI-MS和UV-vis光谱监测表明，[Au9(bisNHC)4Br]2+为关键中间体。此外，我们还合成了含2,4,6-三甲基苄基单元的NHC稳定的环形Au10簇。[Au10(NHC)6Br3]Br簇容易发生转化形成Au25二面体簇，而相应的Cl簇则不发生转化。这一事实可能是由大体积的甲巯基取代的NHC配体所施加的空间环境以及较小的氯配体所引入的空间和电子因素所解释的。

In FY 2022, we successfully synthesized gold nanoclusters stabilized by N-heterocyclic carbene (NHC) ligands in collaboration with the Tsukuda and Hakkinen group. We demonstrated that the use of chiral, BIANP-inspired NHCs to prepare chiral Au10 nanoclusters with a unique elongated central Au10 core. ESI-MS and single-crystal X-ray crystallography confirmed the molecular formula to be [Au10(bisNHC)4Br2]2+. The chiral Au10 nanocluster adopts a linear edge-shared tetrahedral geometry with a prolate shape. The UV-vis spectrum this cluster in CH2Cl2 displayed four prominent absorption bands at 291, 325, and 546 nm, which is a significant departure from the spectra of bis-NHC dinuclear Au(I) complexes. CD spectra demonstrate chirality transfer from the chiral bisNHC ligand to the inner Au10 nanocluster core. The reaction monitoring by ESI-MS and UV-vis spectroscopy indicated the formation of [Au9(bisNHC)4Br]2+ as a key intermediate.In addition, we achieved the synthesis of a toroidal Au10 cluster stabilized by NHC bearing bulky 2,4,6-trimethylbenzyl units. The [Au10(NHC)6Br3]Br cluster readily undergoes conversion to form a biicosahedral Au25 cluster, while the corresponding Cl cluster showed no conversion. This facyt may be explained both by the steric environment imposed by the bulky mesityl-substituted NHC ligand, as well as steric and electronic factors introduced by the smaller chloride ligands.